Currently, various kinds of portable electronic devices are very popular among consumers, resulting in the demand for portable speaker devices. The portable speaker device is small in volume, and so are the speaker and cabinet thereof. The small cabinet tends to produce higher resonance frequency and thereby has weak bass performance. Conventionally, a passive speaker having only a diaphragm and a spider without a magnet is mounted on the small cabinet to improve the bass performance thereof. When the speaker of a portable speaker device vibrates, air inside the cabinet is vibrated, bringing the passive speaker to vibrate at the same time and thereby improve the bass performance of the portable speaker device. However, the improvement of the bass performance brought by the passive speaker is very limited. It is therefore desirable to develop a speaker device that has improved bass performance in the entire low-frequency band instead of being limited to only a few low-frequency points.